1. Field of the Invention
The present invention relates generally to a lens device, and more particularly to a lens device that can be collapsed for a camera with a zooming function.
2. Description of Related Art
A cam mechanism is used to move a lens barrel along an optical axis. The cam mechanism is composed of cam followers formed on the outer periphery of the lens barrel, cam grooves formed on the inner periphery of a rotatable barrel to couple with the cam follower, and guides that prevent rotation of the lens barrel and guide it along the optical axis. Rotation of the rotatable barrel moves the lens barrel along the optical axis due to the cam grooves.
An example of the guides is a fixed barrel with guide slits along the optical axis, and the cam followers are coupled with the guide slits. Another example of the guides is guide bars along the optical axis and sliders formed on the lens barrel, and the sliders are coupled with the guide bars. The applicant of this invention has already proposed a guide method (Japanese Patent Application No. 11-280316). In the guide method, guide grooves are formed on the inner periphery of a first lens barrel, and arms extend from the front of a second lens barrel, and couplers are arranged at the ends of the arms to couple with the guide grooves.
In the guide method, however, if the camera is dropped and a pressure is applied to the arms and the guide grooves, the couplers come off from the guide grooves. Recently, the first lens barrel became thinner and the guide grooves became shallower to make the lens device small in size. Therefore, the couplers easily come off from the guide grooves even if a slight pressure is applied to them.
It is therefore an object of the present invention to provide a lens device which can prevent a guide member from coming off from a guide groove with a simple structure.
The above object can be achieved by providing a lens device comprising: a lens barrel that holds a lens and has a guide groove formed on a periphery of the lens barrel along an optical axis, and a guide member that is coupled with the guide groove to guide the lens barrel along the optical axis; wherein a bottom part of the guide groove is wider than an opening part of the guide groove, and a top part of the guide member is wider than a base part of the guide member.
The above object can be achieved by providing a lens device comprising: a lens barrel that holds a lens, an arm member that is provided along an optical axis and has a guide groove formed on a periphery of the arm member along the optical axis, and a guide member that is coupled with the guide groove to guide the lens barrel along the optical axis; wherein a bottom part of the guide groove is wider than an opening part of the guide groove, and a top part of the guide member is wider than a base part of the guide member.
According to the present invention, the bottom part of the guide groove is wider than the opening part, and the top part of the guide member is wider than the base part. Thus, the guide member does not easily come off from the guide groove even if a pressure is applied to them.